This invention relates to an air filter device arranged in the incoming air flow path of a heating or air-conditioning system of a motor vehicle. When the air flow direction is reversed, the air filter device, which has an assigned fan, is acted upon for the cleaning of the air filter device.
A device of this type in which the fan is arranged in the incoming air flow in front of the air filter device is known from DE-OS No. 30 04 675. In order to clean the air filter device, it is necessary to reverse the rotating direction of the fan, resulting in relatively high costs with respect to wiring technology and increased difficulty in the operation of the device.
It is an objective of the invention to achieve an effective cleaning of the air filter device without reversing the rotational direction of the fan by providing a simple flap construction and arrangement of the wiring.
This objective is achieved by providing an air filter device that is supported by a fan, whereby the fan is placed downstream of the filter with respect to the incoming air flow and whereby at least one flow altering arrangement is positioned downstream of the fan. In this case, the air filter device may consist of a screen that is arranged on the air inlet side and holds back major direct particles, in addition to a filter that is arranged behind it and also separates fine dust. This filter may also contain a filter section, for example, with an activated-carbon filling, that retains toxic substances, substances having a bad odor and other harmful substances.
In one preferred embodiment of the invention, the flow altering arrangement includes a blocking element that is developed as a two-wing flap that is arranged upstream of the heat exchanger surfaces and which selectively blocks and unblocks the fan air flow to the heat exchanger surfaces and to the air filter device. The other wing of the two-wing flap alternately blocks or unblocks an opening to the passenger space.
In another preferred embodiment of the invention, the flow altering arrangement includes a blocking element that is arranged in each duct leading to side nozzles.
The point in time for introducing the cleaning process can be determined by detecting the changing pressure loss values across the air filter device. When a predetermined value is reached, an electrical and/or acoustical signal is triggered.
In another preferred embodiment of the invention, a sensor is arranged downstream of the air filter device that, in the case of a predetermined intensity of a harmful and/or bad-odor substance, triggers an electrical and/or acoustical signal.
According to this preferred embodiment, the signal can be used for the automatic starting of the cleaning phase.
A more intensive cleaning by highly heated air is effected when the signal is not triggered until the cooling water temperature is about 80.degree. C.
According to another preferred embodiment of the invention, a cleaning phase is introduced before the start of the driving or after the end of the driving. According to this preferred embodiment, which can be realized at very low cost, the cleaning phase is introduced independently of the amount of pressure loss and/or of the harmful substance concentration of the air filter device.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.